Of the 91 glaciers being tracked, 84 had retreated in 2005 compared to a year earlier, according to a study by the Swiss Academy of Sciences. The other seven did not change.

The report, released Wednesday, follows earlier ones documenting a long-term melt, posing a threat to Switzerland’s thriving winter sports industry. One ski resort has even wrapped part of its shrinking ice-cap in a giant blanket to try to reduce the summer melt.

Scientists in other parts of the world with glaciers have identified a global pattern. While some glaciers are growing, many more are in retreat. What’s not known is whether the trend is due to nature’s cycles or man’s impact via gases tied to global warming.

The Trift glacier in central Switzerland saw the biggest change last year, retreating by more than 600 feet.

Scientists said the lake that the glacier feeds into had accelerated the retreat by calving ice off and warming the surrounding area.

The 2004-2005 winter season saw lower than average snowfall.

Not only did glaciers lose length, their volume also diminished. The height of three glaciers closely studied in the survey had shrunk by between 27.5 inches and 5.6 feet, predominantly through lower than average snowfall during the 2004-2005 winter season.

The 91 glaciers being tracked are the largest of 1,800 glaciers in Switzerland.